1. Field of the Invention
The present invention relates to the field of communication devices. More particularly, the present invention relates to radio receivers.
2. Description of Related Art
Radio receivers are well known in the art. Typically, a radio receiver intercepts radio frequency (RF) signals by way of an antenna that is coupled to a front end of the radio receiver. The front end of a radio receiver typically includes one or more filters and low-noise amplifiers that receive incoming RF signals. Since signal processing is less complicated for signals at lower frequencies, RF signals are typically down-converted by a mixer before being processed.
Typically, a mixer receives the RF signal to be down-converted and a signal from a local oscillator device (LO) that may have a frequency lower than the frequency of the RF signal. In response to these signals, the mixer produces an intermediate frequency (IF) signal that may further be driven to an IF filter from where a filtered IF signal may be driven to a demodulator, signal processing unit, etc. The IF signal has an amplitude proportional to the amplitude of the RF signal and a frequency typically lower than the frequency of the RF signal. In most radio receivers, the frequency of the IF signal is proportional to the difference between the frequency of the RF signal and the frequency of the local oscillator device.
A dual band radio receiver is a receiver configured to receive signals belonging to two frequencies ranges (bands). For example, in certain multimedia applications, signals belonging to two bands such as data and voice signals may be transmitted intermittently to a dual band radio receiver. The dual band radio receivers that are typically utilized in these applications require two local oscillators, one for each band. Additionally, such dual band radio receivers may require two IF processing devices such as demodulators, amplifiers, signal processors, etc. These dual band radio receivers are expensive due to the utilization of two local oscillators and two IF demodulation stages.
It is desirable to provide a dual band radio receiver at reduced cost. It is also desirable to provide a dual band radio receiver that allows quick switching of a local oscillator device between two high frequency bands that are relatively close to each other.